The present invention relates to a fluorine-containing copolymer and a curable composition containing the same, and more particularly to a fluorine-containing copolymer which is suitable for use in coatings, sealants, films, and the like, and a curable composition containing the copolymer as a main component.
In a field of a fluorine-containing resin coating curable at room temperature, a coating composition containing a polymer comprising as main components a vinyl ester of carboxylic acid having about 10 carbon atoms and a fluoroolefin has been known (Japanese Unexamined Patent Publication No. 61-275311). However, since the fluorine-containing copolymer has a structure wherein an ester group bonds to the polymer main chain, there is a case that the copolymer is easily deteriorated by light. Accordingly, though the coating film thereof is excellent in gloss and water repellency just after coating, they become immediately poor due to the insufficent weatherability of the copolymer. Thus, it is impossible to keep the film appearance excellent for a long period of time.
Also, in the field of the fluorine-containing copolymer, a fluorine-containing copolymer used for a coating which contains a polymer comprising as main components a vinyl ester of carboxylic acid having about 10 carbon atoms and a fluoroolefin and is not required to bake at a high temperature has hitherto been known (Japanese Unexamined Patent Publication No. 59-102962). The coating is used for protecting a base material and for improving the weatherability of the base material. However, since the fluorine-containing copolymer has a structure wherein an ester group bonds to the polymer main chain, the copolymer is easily deteriorated by light. Accordingly, though the coating film thereof is excellent in gloss and water repellency just after coating, they become immediately poor due to the insufficient weatherability of the copolymer. Thus, it is impossible to keep the film surface excellent for a long period of time.
On the other hand, an alternating copolymer of chlorotrifluoroethylene or tetrafluoroethylene, and vinyl ethers wherein one kind of the vinyl ethers has a crosslinkable functional group is excellent in weatherability and is curable at room temperature. Accordingly, it has been proposed to use the alternating copolymer in fluorine-containing resin coatings (Japanese Examined Patent Publication No. 60-21686). The coating containing the alternating fluorine-containing copolymer is, however, inferior in appearance, gloss, solubility, compatibility, hardness, and the like to other widely used coatings. Also, though the alternating copolymer is superior in weatherability and chemical resistance to the fluorine-containing copolymer prepared using the vinyl ethers, as mentioned above, the compatibility with curing agents and the pigment dispersibility are poor. Accordingly, the alternating copolymer cannot be widely used as the coating.
An object of the present invention is to provide a fluorine-containing copolymer which is excellent in solvent solubility and compatibility with curing agents, and which can provide a coating film having excellent appearance, gloss and weatherability, the gloss and the weatherability being able to keep excellent for a long period of time.
A further object of the present invention is to provide a curable composition containing the above-mentioned fluorine-containing copolymer as a main component.
These and other objects of the present invention will become apparent from the description hereinafter.